I've never had any signal problems with mine at all. Always works exactly as it should.
I have a 3G iPad 3 and it does get VERY hot, to the point that I have turned it off for 10 minutes just in case it turns itself off at the critical moment I arrived back in the R112 zone!
It never has switched itself off, but as an Apple expert I would suggest it is not relied upon as a sole gps device due to the thermal shutdown.
I use it along with my old garmin, which I would otherwise have had to replace.
Best one for skydemon is the current iPad 2s, £100 cheaper and have a bigger battery than the original iPad 2 and don't run as hot.